Making tubing



Oct; 1940. B. L. QUARNSTROM 2,216,519

1 MAKING TUBING Filed Jan. 3, 1938 2 Sheets-Sheet l IN VENT OR.

Be rt L. Qua rngtrom ATTORNEY. S

Oct. 1, 1940.

B. L. QuARNs'T-Ro MAKING TUBING 7 Filed Jan. 3, 1938 2 Sheets-Sheet 2OEE INVENTOR.

ant LLQuarnsLrm-n Patented Oct. 1, 1940 0mm; STATE;

This invention has to do with the making of tubing from strip stock, andit is concerned particularly with a method where an electrical currentis passed lengthwise through the tube to seal 5 the seam or seams, or tounite the plies and, if desired, to apply'an exterior metallic coatingto In general, the invention aims to provide improvements in the methodand apparatus where tube is passed with longitudinal movement throughlongitudinally spaced electrodes so that electrical current through andheats successive sections of the tube. At least one of the electrodes,and preferably the one which contacts with the tube where it is in aheated condition, is in the form of a bath of molten metal. This moltenmetal not only serves as an electrode but serves as well to supply themetal for sealing the tube and, where desired, to provide an exteriorcoating. Thus the molten metal electrode is in itself the sealing metal.In this way, the basic metal forming the tube may be bare or uncoatedstock andthe sealing metal or coating metal, or both, is derived fromthe metal which comprises one of the electrodes. Mechanical contact withthe surface of the heated tube, by an electrode either in the form of aroller, shoe or otherwise, is eliminated, as there need be no surfacecontact with the tube as it emerges from the molten bath with thesealingmetal in position in the seam or between the plies, and covering thesurfaces of the tube as a coating. The process lends itself to a speedyoperation, and the sealing-and coating process may be carried out as thetube emerges from a tube mill.

Different metals may be used for the stock and for the sealing andcoating metal. However, as specific examples, it maybe pointed out thatthe strip stock for forming the tube may be of ferrous metal suchas lowcarbon steel, and the sealingand coating metal may be any oneof variousmetals such as copper, tin, zinc, lead, a lead and tin mixture commonlyknown as solder, or a mixture or alloy of any one of the above metals orother metals. The strip stock may be of copper or copper alloy, and thebath of molten metal may be tin, zinc, lead, or an alloy of'these orsimilar metals, or a copper alloy for that matter, but preferably themolten metal which is used should have a melting point lower than thatof metal forming the strip. r

The method and apparatus are somewhat dia grammatically illustrated inthe accompanying Fig. 1 is a view illustrating one form of appa-SFPIATENT "OFFICE 2,216,519

MAKING TUBING .Bcrt L. Qua-matron, Detroit, Mica. assignor to TubingOompany, Detroit, Mlclma corporation of Michigan ratus for making thetubing, the arrangement being that the tube moves in an upwardlyinclined direction. Fig. 2 is a view showing an arrangement where thetube moves vertically. t s

Fig. 3 is a view illustrating the arrangement of an apparatus for movingthe tube horizontally.

Figs; 4 and 5 are cross sectional views taken through tubes of'diflerent types and illustrating diflerent forms of tubes which can bemade of 10 this method. I

In Fig. 1 a tube mill is generally illustrated having rollers I, thistube'mill being of the type generally known to those versed in the art.The tube mill may form a tube of the type illustrated 15' in Fig. 4,which is formed of two strips of stock fashioned with an outer ply 3 andan inner ply 4, each with a seam structure generally illustrated at 5.On the'other hand tubes of other types may be made such as the .tubeillustrated in go Fig. 5 which is of single ply construction with aso-called lock seami. Both tubes are. generally illustrated at 2. Thesetwo forms of tubes are shown merely as examples-of diiferent forms oftubes which can be made by the process, it being 25 understood thatthere are quite a number of diflerent types of seams and different waysof making single and double ply tubing.

The tubing may be passed directly into the seal-, ing unit as it passesfrom the tube mill as-illus- 30 trated in'Fig. 1, although it iswithin'the inven-- tion, to cut the'tubing which passes out of the tubemill into lengths, and to pass the lengths at a'later time, through thesealing unit. There .is an electrode Ill in the form of "a roller'which35 first engages the tube, and the tube may'be held against theelectrode by a roller H.- The other electrode is in the form of a bathoi molten metal i2. A conductor for conducting electrical 1 current tothe two electrodes as illustrated at I3, 40

insulating substance l8.

' The tube enters the molten metal by passing through an inlet device oftubular form and of such internal diameter as to rather snugly fit thetube. This inlet device is preferably lined with a non-conductingmaterial for relatively snugly fitting the tube and is supported by anexterior protection 2| which slidably tits in a projection 22 on thereceptacle 16. The part It may be carried by a bracket 23 mounted forsliding movement in the direction of the extent of the tube. This may bedone by a screw threaded shaft 24 driven through the means of a motor 25connected to the shaft through the several connections shown at 26. Theelectrodes may be located within a housing 21 connected to which is acooler 28 and through which the tube passes as it emerges from the bath.A suitable non-oxidizing or reducing gas may be' maintained within thehousing 21 where the metals employed are such as to require such anatmosphere to avoid oxidization, and this gas may be introduced throughthe inlet 29. The mass of molten metal may be maintained at a properlevel by feeding metal into the same, as for example, by running a wire30 of the metal into the bath from a supply coil 3|. If any of themolten metal should escape between the parts 21 and 22, it may flow intothe drain 32 and be collected in a suitable vessel 33. a

When the device is out of operation the motor 25 may be operated toshift the sleeve 2l2l to a position where its upper end is above thelevel of the molten metal in the vessel I6. This position of the sleeve20-2l is shown by dotted lines in Fig. 1.

In use, the sleeve 202| may be positioned substantially as illustratedin Fig. 1 and as the finished tube leaves the tube mill it is heated byelectrical resistance due to the current passing lengthwise through thetube between the electrodes Hi and i2. The molten metal thus serves asone electrode. At the same time this molten metal flows into the seam sothat upon being cooled the seam is sealed. With the form of tube shownin Fig. 4 the molten metal may not only flow into the outer seam 5 butthe process may be so timed that the metal may flow in between the plies3 and 4 so as to seal the plies together substantially throughout thecontiguous surfaces and to seal the inner seam. As the tube emerges fromthe molten bath it passes into the cooler 28 so that the metals aresufiiciently cooled prior to being introduced into the atmosphere toprevent the formation of deleterious oxides. Of course, the temperaturesused may vary, depending upon what metals are employed. For example,where copper is the molten metal the temperature will have to be highenough to melt the same, but if a lower melting point metal is used,lower temperatures may be employed.

In this manner, the tube is heated prior to being introduced into themolten metal so that it is conditioned by the preheating to properlyreceive the metal for soldering, tinning or brazing purposes as the casemay be. The tube passes through the molten metal without substantialfriction and without mechanical contact with the hot tube; that is tosay, mechanical from the standpoint of an electrode in the form of aroller or shoe contacting with the hot tube or molten coating. Thuswhere a coating is applied to the tube it is not rendered rough orimperfect or defective by mechanical contact therewith. Nothing touchesthe tube on its exterior surface after it becomes heated until it haspassed out of the cooler and the the coating metal is solidified. Theelectrode l0 and the opposing roller ll engage the tube at a point whereit is relatively cold so that there is no difliculty with mechanicalcontact at this point. By disposing the apparatus so that the tubeextends angularly upwardly, the vessel I6 may be disposed at an angleand this permits of the sleeve Ill-4| to act as a valve as abovedescribed.

The variation shown in Fig.2 embodies generally the same parts and thereference characters applied above are applied to corresponding parts inthis form, and thus duplication of description is avoided. A furthervariation shown in this view is that of moving the sleeve structure 2|hydraulically. The motor 25 is connected to a hydraulic pump which is intum connected by tube lines ll and 42 to opposite ends of a cylinder 4!having a piston therein (not shown). A piston rod 44 connects to thebracket 23. Of course, it is to be understood that this hydraulicshifting arrangement may be used in the inclined form shown in Fig. 1,and the screw threaded rod arrangement may be used with the verticalform shown in Fig. 2.

A horizontal arrangement is shown in Fig. 3, and here again the samereference characters are applied to similar parts. In this form thevessel Iia has a closed bottom and the tube enters and leaves the samethrough an inlet 45 and an outlet 48, and any metal which escapes fallsinto the drain 4! and is conducted out of the chamber 21 by a tube Iwhere the metal may be collected in a vessel 48.

In accordance with this invention, it is preferred that the tubeimmediately pass into the sealing and coating apparatus as it leaves thetube mill. The tube mill passes the tube at a relatively high speed, anddue to the fact that the tube is heated by electrical resistance it maybe brought up to a proper temperature for receiving the molten metalwhile it is moving at this high speed. In this regard the distancebetween the first electrode and the molten metal electrode may belengthened or shortened, and also the heating current may be varied asto voltage or amperage to obtain the desired preheating action on thetube. The reducing atmosphere functions to reduce oxides on the tubewhere this is necessary, and to prevent formation of oxides, and in thissense functions as a so-called flux. With some metals an arrangement maybe used for applying a flux to a tube rather than maintaining the tubein a non-oxidizing or reducing atmosphere. In either case, the tube maybe said to be in a non-oxidizing or reducing environment.

I claim:

1. In the method of making tubing fashioned from strip metal stock, thesteps of moving the tubing longitudinally through a bath of molten metalwhich flows into the seam of the tube, passing an electrical currentthrough the molten metal, across the contact between the molten metaland the tube, and through successive sec tions of the tube as thesections approach the molten metal bath to heat the tube preparatory tothe reception of the molten metal in the bath, and then cooling the tubeto seal the seam.

2. In the method of making tubing fashioned from strip metal stock, thesteps of maintaining a body of sealing and coating metal in a moltencondition, connecting the body of molten metal in an electrical circuit,passing the tube lengthwise through the bath of molten metal,establishing an electrical contact with the moving tube at a pointspaced lengthwise of the tube and in advance of the bath of molten metalwhereby a circuit is completed by successive sections of the moving tubewith the molten metal serving as an electrode, and passing an electricalcurrent through the bath and successive sections of the tube for heatingthe successive sections prior to passage through the molten metal forsealing the seam and coating the tube, and then cooling the tube tosolidify the molten metal.

3. In the method of making tubing fashioned from strip metal stock, thesteps of maintaining a body of sealing and coating metal in a moltencondition, connecting the body of molten metal in an electrical circuit,passing the tube lengthwise through the bath of molten metal with astraight line movement and with the tube contacting only with the moltenmetal while in the bath, establishing an electrical contact mechanicallywith the moving tube at a point spaced lengthwise of the tube and inadvance of the bath of molten metal whereby the circuit is completed bysuccessive sections of the moving tube, passing an electrical currentthrough the bath and successive sections of the tube for heating thesuccessive sections prior to passage through the molten metal forsealing the seam and coating the tube, cooling the tube and maintaininga non-oxidizing environment around the tube during the heating thereof,during its passage through the bath and during the cooling until themolten metal is solidified.

4. An apparatus for sealing the seam of a tube fashioned from stripstock and for coating the exterior surfaces of the tube comprising, abath of molten sealing and coating metal, means for passing the tubethrough the bath, an electrode contacting with the tube at a point inadvance of the bath of molten metal, and means providing a circuit foran electrical current for heating successive sections of the tube priorto passage through the bath comprising electrical conductors inelectrical connection with the bath of molten metal and the electrode 5.An apparatus for sealing the seam of a tube fashioned from strip stockand for coating the exterior surfaces of the tube comprising, a bath ofmolten sealing and coating metal, means for passing the tubetherethrough including an entrance for the tube located below the levelof the molten metal, an electrode contacting with the tube at a point inadvance of the bath of molten metal, means providing a circuit for anelectrical current for heating successive sections of the tube prior topassage through the bath comprising electrical conductors in electricalconnection with the bath of molten metal and the electrode, a chambersurrounding the bath of molten metal, a cooler into which the tube movesas it emerges from the bath of molten metal, and means for maintaining anon-oxidizing environment in the chamber and cooler.

6. An apparatus for'coating the exterior surface of a tube comprising, abath of molten coating metal, means for passing a tube with lengthwisemovement through the same, an electrode positioned to contact with thetube in advance of the bath of molten metal, means providing a circuitfor an electrical current for heating successive sections of the tubingby electrical resistance prior to passage through the bath of moltenmetal comprising conductors having an electrical connection with theelectrode and with the molten metal bath.

BERT L. QUARNSTROM.

